Chapter 9, Problem 10RQ

Interpretation Introduction

Interpretation:

• The following observation has to be explained – Enthalpy of vaporization of water is greater than the enthalpy of fusion.

• The change in intermolecular forces when a solid goes to liquid to vapor state has to be explained.

• The meaning of “volatile liquid” has to be outlined.

• The vapor pressure of volatile liquids at room temperature has to be illustrated.

• The strength of intermolecular forces in highly volatile liquids has to be outlined.

Concept introduction:

In all the three states of matter, the constituents (molecules or ions) of the matter do possess forces between them which are not the same in each state. These forces are called intermolecular forces. The intermolecular forces are relatively strong in the solids than liquids and weaker in the gaseous substances. This variation influences many of the properties of all the three distinct states of the matter. If the strength of intermolecular force is high in a substance then its melting point, freezing point, boiling point will be high and the vapor pressure will be low. If the strength of intermolecular force is very low in a substance then it can vaporize easily. Such phenomenon is knows as volatility.

The amount of energy required by a liquid to convert a quantity of it to vapor at constant pressure is defined as enthalpy of vaporization. During vaporization, the pressure exerted by the vapor state existing in equilibrium with the liquid state is known as vapor pressure of the liquid.

The amount of energy required by a solid to convert its certain quantity to liquid under constant pressure is defined as enthalpy of fusion.